Yes. Home theatre satellites connect through a private link to the master device. They don’t connect directly to WiFi.

Does your router offer a view of the arp table? All devices should be visible there.

You might see it using a network command like “arp -a” that lists devices seen on your network regardless of how they connected. Or if not available on newer Linux try “ip neighbour”

My era 300’s will sometimes show as connected and sometimes my sub shows connected to my WiFi network. They all work but strange that one person says they connect on a private network but I see them on my WiFi network.  I did have to use the home WiFi to set them up. 
 

Moderators can delete this thread. 

They connect through the soundbar, but will have their own ip on your network.